With increasing demand for data, voice/audio, video and other services, such as high-definition Internet protocol television (IPTV) and multi-media release systems, demanding higher bandwidth for passive optical network access technology is widely applied. A passive optical network (PON) refers to an optical distribution network (ODN) with neither active electronic network devices nor a dedicated electronic power supply. However, since the ODN does not require any active electronic devices, the ODN uses one or more passive devices, such as a splitter.
Typically, the passive optical network includes (i) an optical line terminal (OLT) unit that is located in a central control station, and (ii) a number of corresponding optical network units (ONUs) that are located in end user units. Generally, between the OLT and the ONU, the ODN includes fibers and a passive optical splitter or coupler.
In general, OTDR technology can be used to monitor fiber performance (e.g., to monitor or determine the occurrence of fiber fusion splices, connections, or breakages). Optical pulse signals are transmitted or input to a fiber input terminal. Then, fiber-reflected optical signals are collected at a high speed at or from the fiber input terminal to obtain a series of sample data points. Each sample data point represents a reflected optical power at a certain point in the fiber. The relationship between fiber attenuation and fiber length is obtained by plotting the distance between the fiber input terminal and each sample data point along the abscissa (e.g., x-axis) and the reflected optical power value of each sampling point along the ordinate (e.g., y-axis), so that the performance (e.g., reflected optical power as a function of distance) of the tested fiber can be determined.
FIG. 1 shows a conventional passive optical network 100 including an optical time domain reflectometer (OTDR) 110 that monitors the network 100. The OTDR equipment 110 couples a test signal into a passive optical network (PON) through a wavelength division multiplexing (WDM) system 120. The WDM system 120 is located outside of the optical line terminal (OLT) 130. In the PON system 100, a signal 140 having a wavelength of 1490 nm is issued by the OLT 130 to each optical network terminal (ONT) or optical network unit (ONU) 140-149 via corresponding fibers 125 and 161-169 through a splitter 160. The operating wavelength of the ONUs 140-149 is 1310 nm. Each ONU 141-149 can send data to the OLT 130 through a time division multiplexer (TDM; not shown). A signal 115 from the OTDR equipment 110 has a wavelength of 1625 nm, which is transmitted or inputted into the fiber 125 via the WDM to test the performance of the fiber.
FIG. 2 shows a conventional OLT 130. The major external signals for the optical transceiver 130 include a transmitter signal (TX) 201, a receiver signal (RX) 202, and an inter-integrated circuit (IIC) signal 203. The TX signal 201 is a high speed signal sent to the optical transceiver 130 from an external device to a driver 204, which drives a laser 206 to transmit a beam having a wavelength of 1490 nm into a fiber 240, and subsequently output via WDM 220. The WDM 220 also produces and/or transmits a beam having a wavelength of 1310 nm to a receiver 207 via a fiber 250. The beam is converted into an electronic signal and output as a high speed RX signal 202 through a limiting amplifier 205. The limiting amplifier 205 amplifies and reshapes the received signal 235 from the optical device 230. An inter-integrated circuit interface 203 coupled with a microcontroller unit (MCU) 208 is used for the optical transceiver 230, which monitors data and reports the same to an external device (not shown) over the IIC interface 203.
Referring back to FIG. 1, the conventional passive optical network 100 uses existing equipment currently on the market. Generally, the OTDR equipment 110 is relatively expensive and difficult for placement and wiring in a server room, especially when adding additional WDMs 120 and OTDR equipment 110 to the conventional passive optical network 100.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.